Cyclobenzaprine, or 3-(5H-dibenzo[a,d]cyclohepten-5-ylidene)-N,N-dimethyl-1-propanamine, was first approved by the U.S. Food and Drug Administration in 1977 for the treatment of acute muscle spasms of local origin. (Katz, W., et al., Clinical Therapeutics 10:216-228 (1988)). Amitriptyline, or 3-(10,11-dihydro-5H-dibenzo [a,d] cycloheptene-5-ylidene)-N,N-dimethyl-1-propanamine, was first approved by the U.S. Food and Drug Administration for the treatment of depression.
Subsequent studies have shown cyclobenzaprine to also be effective in the treatment of fibromyalgia syndrome, post-traumatic stress disorder (PTSD), traumatic brain injury (TBI), generalized anxiety disorder and depression. Furthermore, the utility of cyclobenzaprine as an agent for improving the quality of sleep, as a sleep deepener, or for treating sleep disturbances has been investigated. However, while FDA-approved therapeutics address pain and mood, there are currently no FDA-approved treatments that address the disturbed sleep and fatigue associated with fibromyalgia syndrome. Treatment with cyclobenzaprine may be particularly useful in treating sleep disturbances caused by, exacerbated by, or associated with fibromyalgia syndrome, prolonged fatigue, chronic fatigue, chronic fatigue syndrome, a sleep disorder, a psychogenic pain disorder, chronic pain syndrome (type II), the administration of a drug, autoimmune disease, stress or anxiety, or for treating an illness caused by or exacerbated by sleep disturbances, and symptoms of such illness. See, for example, U.S. Pat. Nos. 6,395,788 and 6,358,944, incorporated herein by reference.
Cyclobenzaprine HCl or Amitriptyline HCl Active Pharmaceutical Ingredients (or APIs) are stable in pill, tablet or capsule formulations for oral administration when combined with certain excipients. However, Cyclobenzaprine HCl or Amitriptyline HCl have slow absorption when ingested by mouth (per oral, or po). To speed absorption, tablets containing Cyclobenzaprine HCl or Amitriptyline HCl have been formulated in various sublingual (SL) preparations. However, both sublingual and oral formulations can have issues with the stability of the APIs and the physical compositions themselves, especially when a basifying agent (a chemical compound that increases the pH of solutions after dissolution of Cyclobenzaprine HCl or Amitriptyline HCl) is present. Therefore, a method or composition that increases stability of Cyclobenzaprine HCl or Amitriptyline HCl (with or without the presence of a basifying agent) in a formulation would be useful.